Master cylinder



J. G. HAWLEY MASTER CYLINDER June 29, 194s.

'3 Sheets-Sheet 1 Filed Oct. 27, 1941 ,Marg

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J. G. HAWLEY MASTER CYLINDER June 29, v194s.

5 Sheets-Sheet 2 Filed 0G11. 27, 1941 M. 4% M$ @mi NN mwv, MMR N. sw Swway// June 29, 1948.

J; G. HAWLY MASTER CYLINDERv 3 Sheets-Sheet 3 Filed Oct. V27', 1941 @mwkw kan@ Jsse awww

Patented June 29, 1948 1arteN stmt-ss NT yori-lola;

This inventionrelates toV the art Yof power,

units,` and Ymore,,particularl'yA to an. .mpeved master cylinder.

Numerous master cylinders ,haveblevously been developed, .but vmost, of-v these have4 been .of coinplicated construction and'. L dependent uponvalveV mechanisms, with the ,resultant tendency to leakage. s Y

I have `found `these L,di'.lii,,culti-es can, ,be `overco'rneand amaster `cylinder can Abe produced Whichjss `simple ,in design efcientinpperation, and relatively inexpensive, vto produce, by `the con,-struction disclosed.herein` It istherefor an object of `this inventiontoprovide a new` and improvedmaster cylinrier.'`

Itis `another object4 to. provide .a mechanically operated mastercylinder.

It is a furtherobject to provide arnaster` cylin` der which vis capableof producing .any ,desired hydraulic pressure.

It is an additional object ,to providea master cylinder` which isf freeyof `valve rnechanisrns.` s

Itis Valsoian object toprcvide `a simple and inexpensive, singleplunger,` direct acting master cylinder ofgeneral utility. s

Withr the above and other objects in .view, which" will be apparent `asthe description proceeds, I have set Aforth ,my invention injthefolj-`lowing i, specification and 1 have` illustrated `,it in the accompanyingdrawings, in which:

Figure 1 is a plfanvieW-of rnyfneivmaster cylinder in uncompressedposition; y

Fig. 2 is a longitudinal `vertical `section on the lineup-2 of Figli;

Fig. 3 is a corresponding vertical Ysection,but

Withthemaster `cylinder in cornpletelycorrieV pressed position; y

Fig;` 4 is a transverse verticaljs'ection on the line 4er-4 of Fig. 3;

Fig. y5` is Aa' transverse vertical section, on an enlarged scale, onthe-'line `Sell of Eigsfland 3;

1 Fig. `6Y Vis f al longitudinal vertical section, on an enlargedscale,` througlra sleeve;` i

Figi 7 isa longitudinal vertical sectonof a modification; vand s Fig 8is a transverse vertical section onthe line-8&8 of Figx'l. t

Referring to the accompanying-drawinga `and particularly'to Figs-l and2therecLpne ein bodiment ofjiny improvedjmaster cylinder 2U preferablycomprises a fluid cylinderv 2i, a high pressure `fluid chamber unit22,anda lbllllg'erA 23.

best shown in Figs.f2 and 3, iluid cylinderv 2 I g and high i pressure@fluid chamber Vunil', 22 i are preiferablyV formedintegrally asahousing i3u,

2. Whichfalso has a boss 3l, internally threaded at 32 to receive acorrespondingly threaded end 33 of a pipe 34, which constitutes areservoir 35 for the operating fluid (not shown). As also shown in Figs.2 and 3, the outer end of the reservoir 35 is internally. threaded at 36to receive-a correspondingly threaded closure plug 3l. The latter isvented at 3 .8 to maintain suilicient contact With the atmosphere tocause the fluid to be fed into the uid cylinder 2| lby gravity. Althoughn0 operating fluid has beenshown it will be understood that any suitable`operating iluid may be used.

The housing 3i) is recessed at 40 to form ,the bore of the iluidcylinder 2|, and is providedvvith a reduced diameter counterboreytl toprovide aV fluid receiving recess,yand is further counterbored at 42 toprovide the chamber of the high pressure fluid chamber unit 22, which isclosed at its far end 43.

l In practice,` I prefer to make the bore l2 of the high pressure fluidchamber unit 22 of slightly greater diameter than the diameter of theplunger 23 to allow the latter to move freely into the former. When theplunger 23 is 1/2" in diameter, I have found that the bore 42 of thehigh pressure fluid chamber unit may conveniently be madeg". s

The boss 3| `of housing 3E! is provided With a feed holeMtocommunicatewith the bore of the cylinder 2 l. l

As shown in Fig. 5, housing 30 also has an internally threaded boss 39v.which communicates with .a transverse orifice 45 that opens intocounterbore 4I. Threaded boss 39 is adapted to receive anyl convenientfitting 46 for the attachment of a tube or pipe (not shown) leading tothe brakes, or other `object to be actuated by the master cylinder. Asshown, this orice 45 communicates Withthe counterbre 4| for thedischarge of the operating fluid when the plunger 23 is operated,iasexplainedbelovv.

I provide a sleeve 4l of just sufficiently smaller diameterthan-the mainbore of the fluid cylinder `2l to `enable it to be inserted into and tofill a substantial portion of that bore and `to act as a bearing for theinner end of the plunger 23, this sleeve lbeing provided with a bore 48ofjust suilicient diameter-toi allowthe plunger 23to slide freelytherethrough. I also provide the sleeve with aplurality of orifices 5Dcommunieating with the feed hole` Mqthat communicates with the reservoir35.`

A closure :plug 5i threaded at V52 to engage `the internalV threads 49`at thefree end of the hous-r 3 ing 38, is provided to constitute a headfor my master cylinder. Plug 5| is provided with a bore 48 of the samediameter as the bore 48 in sleeve 41 to form an additional guide bearingfor the plunger 23. Suitable gaskets 53 and 54 are provided at theopposite ends of the sleeve `41 to prevent leakage of fluid past theplunger as the latter is reciprocated. An auxiliary metal washer 55 isprovided between the gasket 54 and the end of the closure plug 5| toprevent twisting the gasket when the plug is tightened. The closure plugis also preferably provided 'with an end recess 58, in which a washer 51is inserted to act as a wiper and keep the plunger free from dust anddirt. Washer 51 may be of any desired type, but is preferably a combinedrubber-felt washer with the felt side placed against the closure plug5|.

As best shown in Figs. 2, 3, and 6, the sleeve 41 is provided with areduced diameter portion 58 extending entirely around its periphery, ex-

tion with an anti-airlock recess 65'that -communicates with thereservoir 35. By providing a series of these oriiices 58 and 54, therewill always be communication regardless of the circumferential positionof the sleeve 41.

A plate 68, provided with two internally threadedbosses 59 and 10, is.provided to act as a pedal, boss 69 receiving the threaded end 1| ofplunger 23. The plunger is also provided with coiled-compression springs1:2 and 13 which are telescoped therearound and separated by a springguide 14. The outer end of spring 12 bears against a recess on theclosure plug 5| and the outer end of spring 13 bears against the boss 69on plate 68 to constitute means for normally retracting the plunger.

The outward travel of the latter is controlled by a pedal stop 15 lwhichis threaded atene end 11 to be received in the boss 10 of the plate 68.At its opposite end, the pedal stop is preferably provided with a screwplug 18 that is threaded into the end of the pedal stop.

As best shown in Figs. 1 and 4, the housing 38 is also provided with anintegral peripheral flange 80 -of any desired shape, but here shown asbeing triangular. It has a plurality of orices 8| for convenience inattaching the master cylinder in any suitable location, such as the oorboard (not shown) of an automobile. It is also provided with anadditi-onal orifice 82 through which the pedal stop 16 passes, the headof the screw plug 18 serving to stop further withdrawal of the plunger,under the influence of ycoil springs 12 and 13, by contacting with thetriangular flange 80.

As best shown in Figs. 2 and 3, the fluid from reservoir passes throughregistering orifices 44 and 58 into the bore 48 ofthe uid cylinder 2|under the influence of gravity, when the plunger 23 is withdrawn to theposition shown in Fig. 2 by coil springs 12 and 113. This tends to llany vacant space in either the fluid cylinder 2| or the communicatingcounterbore 4| and the fbore 42 of high pressure fluid chamber unit 22.

When it is desired to operate the master cylin- A der 28, the operatorpushes lon the pedal plate 68 and forces the plunger 23 inwardly intothe housing 30 against the pressure of coil springs 12 and 13. When theplunger is advanced slightly beyond the point shown in Fig. 2, it cutsoff further entrance of operating fluid into the counterbore 4| and highpressure fluid chamber unit 22 and displaces an amount of fluid equal tothe amount of its penetration beyond the cut-ont` point, thus forcingthe desired amount of fluid out of the counterbore 4| and the highpressure fluid chamber unit 22 through orifice 45 leading to the brakesor other device to be actuated thereby.

As soon as kthe pressure is removed from the pedal 68, coil springs12and 13 withdraw the plunger 23, thus creating a vacuum in thecommunicating bores which causes some fluid to be withdrawn from theconnections leading to the brakes, or -other apparatus being actuated,through the orifice 45. After the plunger 23 has been retractedsufficiently to uncover orices 50, the vacuum allows additional uid toflow from the reservoir 35 to ll any void thus created in fluid cylinder2| or fluid chamber unit 22, because the fluid in reservoir 35 is underatmospheric pressure through vent 38.

In Figs. 'I and 8, I have shown another embodiment of my invention whichis preferred where especially high pressures are to be developed in thehigh pressure fluid chamber unit.

As shown, in this modification I utilize a master cylinder |20, whichcomprises afluid cylinder |2 I, a high pressure fluid chamber unit |22,and a plunger |23. These parts generally conform to those in theembodiment already described, except that plunger |23 is provided with abore |24 and a 'bleeder |25 adjacent to a pedal plate |68.

In this embodiment, the external springs 'l2 and 13 are replaced by asingle spring |12, which is housed in plunger |23 and high pressurefluid chamber unit |22. At one end, spring |12 bears against a recess|26 in plunger |23 near the plate |58 and at its opposite end againstthe head |21 of a spring guide |28 that is forced against the closed end|43 of high pressure uid chamber unit |22 by spring |12. As shown, thespring guide |28 is preferably a small diameter rod, to the other end ofwhich is riveted a washer that constitutes the head |21. Thisconstruction provides a longer spring and facilitates getting an eventension for the entire travel of the plunger while allowing it to moveits full distance in the high pressure fluid chamber unit.

The bore |24 of plunger |23 is, of course, kept filled with theoperating fluid (not shown), and its action is just the same as if itwere solid. VThe bleeder |25 permits the removal of any trapped air.

In this embodiment, the sleeve 41 is vreplaced by a sleeve |41 ofsimilar shape, except that it has a bore |48 of greater diameter thanthel bore 48 of the previous embodiment to provide a larger fluidchamber around plunger |23 and remove any possibility of sucking .airinto the line between the plunger |23 and the sleeve |41 when theplunger return is quicker .than the return of the fluid from the brakes.Sleeve |41 is provided with a plurality of orices |50 for cooperationwith an aperture |44, in the lluid cylinder |2|, that communicates witha reservoir |35.

The embodiment shown in Figs. '1 and 8 also provides vadditional meansforsealing Vthe high pressure fluid chamberunit |22 and preventing anyuid from being by-,passed around the outside of the gasket 53 of theprevious embodiment. rlhis is accomplished by chamfering the end |6| ofsleeve |41, preferably at a 45 angle, and using a rubber gasket |53which is molded to conform to the shape of the chamfered end |6l ofsleeve |41. With this construction, the more pressure developed in thehigh pressure fluid chamber unit |22, the tighter this 45 wedge, formedby the gasket |53, is sealed. This construction may be used with eitherembodiment of my invention.

The other parts of the modica-tion illustrated in Figs. 7 and 8 conformin general to the corresponding parts in Figs. 1-6, and the operationwill be clear from the foregoing description.

It will thus be apparent that I have developed a single plunger, directacting master cylinder of exceedingly simple construction which is freeof valves, which comprises mainly cast or drilled parts, or ordinarydrill rod, thus eliminating vthe necessity for expensive machining. Theonly parts needing reaming are the bores 48 in sleeve 41 and closureplug 5|, the bore |24 in plunger |23, and the bore |48 in sleeve |41.

rIt will also be apparent that this construction results in theproduction .of an immense pressure in the high pressure fluid chamberunit, which may be increased to any desired amount by increasing thetravel of the operating pedal. There are no parts to get out of order orvalves to be replaced, and there is no danger of leakage.

While the parts can be made of more expensive materials than thosedisclosed, it Will be apparent that, for most purposes, this isunnecessary, and that the master cylinder disclosed is a highlyefficient and yet inexpensive construction.

As many apparently widely different embodiments of this invention may bemade without departing from the .spirit threeof, it is to be understoodthat I do not limit myself to the foregoing embodiments or descriptionexcept as indicated in the following claim.

A ma-ster cylinder, comprising a cylinder', a high pressure uid chamber,an outlet, a sleeve of ,substantallythe same diameter as the cylinder,the sleeve having a bore the forward end of which is of reduceddiameter, a plunger of substantially the same diameter as the forwardend of the bore of the sleeve for expelling fluid from said bore andfrom the high pressure uid chamber through said outlet, and means forsealing the high pressure uid chamber, said means comprising a gasketprovided with a wedge-shaped edge for `cooperation with a wedge-shapedseat on the sleeve and adapted t-o form a tight-er 't when the pressureis increased in the high pressure uid chamber.

JESSE G. HAWLEY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

